1. Field of the Invention
The present invention relates to a linear guide device adapted for use in an extreme environment such as a cosmic space or vacuum environment.
2. Discussion of the Background
In general, a space craft such as an artificial satellite is provided with various types of equipment devices, including an antenna device, and a conventional linear guide device is built on each of the liner driving mechanisms or the like for these devices. The linear guide device has a structure in which a pair of guide grooves are provided so as to interpose a guide rail for the main rail, between the guide grooves, and a slider is engaged with the guide rail of the main rail to be linearly movable.
In the slider, a ball circulating path having a ring-like shape, is formed so as to correspond to a ball guide groove of the main rail. In the ball circulating path, a plurality of balls are housed to be movable therein as they rotate. The ball circulating path has an opening at a predetermined position, so as to oppose to the ball guide groove of the main rail. With this structure, when the slider is urged to move in the direction of the rail guide portion of the main rail, these balls in the circulating path move as they rotate. When they move, some of these balls are brought into contact with the ball guide groove of the main rail, and therefore a linear motion is allowed.
However, in the case where the linear guide device of the type described above, is used in a cosmic space of a ultra-high temperature vacuum environment, it is very difficult to employ the general lubricating method using oil or grease, though it can be normally employed on the ground. Instead, for the linear guide device used in a cosmic space, a so-called solid lubricating method is employed for lubricating the members of the device. With this method, a solid lubricating film, which is made of a solid lubricant such as molybdenum disulfide, is formed on the ball guide groove of the main rail, the surface of each ball and the ball circulating path, by the spattering technique, ion-plating, or the plating or coating technique.
However, in the case where a solid lubricating film is formed by the former ones, that is, spattering or ion-plating technique, the linear guide device entails the following drawback. That is, although it is possible to form such a film on the ball guide groove of the main rail or the ball circulating path of the slider, to have predetermined thickness and size, the film cannot be easily formed with high precision on the surface of such a small ball. Therefore, the absolute amount of the solid lubricating film is always too short, which results in short life.
In the case where a solid lubricating film is formed by the latter ones, that is, the plating or coating technique, it is very difficult to prepare a thin film, and therefore powdery materials are easily created due to abrasion. Consequently, a so-called rattle occurs between the slider and the main rail, which further creates abrasion powdery materials. As a result, the friction resistance acting between each other is increased, making it easier to decrease the precision.
The above-described drawback also occurs in an extreme environment on the ground, such as a vacuum atmosphere where oil or grease cannot be easily used as a lubricant.